Internal combustion engines have had over 100 years of development and are clean, reliable, power dense where desired, and fuel efficient where desired. Piston engines have dominated automotive applications with gasoline engines being used more than diesel engines in the US. Automotive engines are undergoing rapid development to increase fuel efficiency to meet regulations. Longer ratios of the stroke relative to the bore, turbocharging, and use of the Miller or Atkinison cycles are technologies promoting efficiency. The goal of this invention is a more fuel efficient engine with inherently good pollution control properties.
Diesel engines are generally more fuel efficient than gasoline but are losing favor in automotive applications due to extra pollution control technology. Two-cycle engines have not been significant in automotive applications but have a long history of use in truck, locomotive, and large marine applications where their fuel efficiency had a good history. Pollution restrictions have particularly hurt fuel efficiency of these two cycle diesel engines and new designs now use four cycle engines. Turbocharging was critical to two-cycle diesel engine efficiency. The ElectroMotive Diesel Div. of Caterpillar (formerly ElectroMotive Div. GM) two-cycle locomotive engine designed an overrunning clutch mechanism which allowed a single turbocharger to operate coupled to the crankshaft at light loads and then uncouple from the crankshaft and operate much higher rpm once exhaust gas pressure built sufficiently. When gas pressure created more torque from the turbine than that applied by the shaft the overrunning clutch roller elements were moved to clearance positions and thus allowed the turbine to freewheel on the shaft. This EMD design of this successful overrunning clutch was essentially that of Dietrich Reister Herzgenaurach and Wolfgang Pfluenger in U.S. Pat. No. 3,537,555 (ref. 1). A similar overrunning clutch system, with an additional feature, is perhaps the most important mechanism for the concept of the Tangential Force Internal Combustion Engine (TFICE) of this patent.
Natural gas, propane, and landfill gas engines have been used in various applications for highly targeted reasons. Hydrogen is being used as a fuel for novel power sources in autos where pollution control laws are strictest. Battery fueled autos are gaining in numbers as are hybrid versions utilizing highly efficient gasoline engines. The Wankel engine is a rotary engine with no pistons or connecting rods and few moving parts. It has been successfully used in niche sports cars where light weight and good power density are beneficial (ref. 2). Emission challenges and low fuel efficiency kept this as a niche engine.
The jet engine was first used in airplanes late in WWII with the Messerschmitt ME262 in 1944. Frank Whittle of England was granted a patent for his turbo-jet engine in 1932. (ref 3). Today's gas turbine engines can have good fuel efficiency but at the high cost of multiple compressor and turbine stages. Gas turbine engines are used where weight and power density are prime concerns.
The present invention is hoped to have potentially significantly higher fuel efficiency than piston engines. The present invention couples force from the power cycle more directly to the output shaft as useable torque. A power vane is attached to the shaft through an overrunning clutch mechanism which allows 100% of the combustion force to be transmitted as usable torque to the shaft for essentially the entire duration of this power cycle. A piston engine design transmits only a fraction of the available connecting rod force into shaft torque because the force vectors need to be resolved to that which is tangential to the crankshaft. Such force vectoring is required at both the piston pin and crankpin. The remaining non-tangential load vectors lead to inefficiencies and unwanted localized forces which produce no desirable effect.
Piston thrust loading and high compressive forces directly into the crankshaft bearings are two unwanted but unavoidable forces in piston engines. The present invention eliminates such unwanted force vectors. Piston thrust loads are sometimes manifested as piston skirt seizures. The fact that the largest diesel piston engines use crossheads to avoid potential piston issues from such thrust loading recognizes this situation. The piston assembly of the TFICE engine will have complexity of its own as it will need to locally match the overall—toroid chamber shape and carry multiple sealing rings. But TFICE “pistons” operate on vanes that transfer torque more directly to the shaft through a symmetrical OCS mechanism mentioned earlier. Said OCS mechanism clutches a multitude of symmetrically spaced roller elements between the vane (or an OCS “housing” securely fitted into the vane) and the shaft. This clutching action transmits torque directly instead of producing a compressive force onto an offset crankpin. Certainly the OCS produces highly localized compressive forces (creating contact stress on and around roller elements) but this is the mechanism for creating moments directly into the shaft. This clutching mechanism is an efficient means to create pure moments and is thought to be much more efficient at converting combustion forces into shaft torque than crankpin offsets and resolving forces.
Other unwanted forces in modern reciprocating piston engines produce crankshaft orbit as various reciprocating weights, crankpin throw angles, and various levels of balance weights produce sometimes unexpected forces on main and conrod bearings. Unit loading is typically high on conrod bearings, especially for the most highly fuel efficient diesel engines. Proper sizing and material choices are needed to avoid seizure or early wear out. Conrod bearings are commonly replaced at half the life of main bearings. The need to change crankshaft bearing increases with increased power and fuel efficiency and so designs are made for wear element components to be replaced instead of more expensive components. Similarly this TFICE invention would ultimately need roller elements and other local wear components designed-in to avoid replacement of higher cost components.
The Wankel rotary engine uses an eccentric shaft and, like the piston engine, combustion forces do not vector directly to the shaft as torque. More combustion force is lost in Wankel engines compared to the TFICE engine being proposed. This engine is also thought to be inherently inferior to the piston engine in regards to fuel efficiency.
Jet engines or turbojet engines have combustion gas flow paths that efficiently resolve vectors into shaft torque via controlled gas flow paths. However the most basic gas turbine engine does not have a simple, fully enclosed combustion process. Certainly modern jet engines are powerful and even fuel efficient with modern design utilizing multiple compressor and turbine stages and ever higher local temperatures. These design features precludes the use of fuel efficient gas turbines from any cost sensitive application.
Piston engines are fuel efficient via achieving relatively high combustion pressures that are contained in a fully enclosed combustion chamber. A reaction component to the force produced on the crankpin in a piston engine is the cylinder head and this fully encloses the combustion process. As the head is fixed via bolts to the block it thus serves as the torque reaction component. The torque reaction in the present invention is the reaction vane as it is pinned to the engine housing. In this manner the combustion torque has an effective reaction torque for mechanical equilibrium.
No forces in the TFICE invention create piston thrust forces or compressive forces into the support bearings. Pure tension or compression is not present in the vanes as combustion forces are tangential to the shaft and there is no reciprocating motion. Essentially, the vanes are either directly connected to the output shaft or the vane rides on roller elements on the shaft. Roller element bearings are envisioned in shaft support roles as these bearings have essentially no compressive or axial forces to contend with. Roller element bearings are another source of fuel efficiency compare to piston engines.
It is acknowledged that the design shown by example herein provides just 75 degrees of power duration cycle compared to the approximately 180 degrees in piston engines. Increasing this duration is possible with different timing and shaft gear ratios. However the TFICE invention is thought to provide much more useful work during the power duration such that small “cylinder (i.e. toroidal chamber) displacements” will produce relatively large torques.
The most pressing design challenge with the present invention is combustion sealing as the Power Vane leaves a growing inside gap as it rotates around the toroid. The invention shown herein explains basic operating principles and only a rudimentary combustion seal is proposed. The topic of combustion sealing will need to be addressed in more detail in the future. The seal shown herein is a series of sealing elements but it seems possible to use a continuous sealing assembly that would fit inside vanes that are locally hollow at this seal. If a continuous seal were developed then efficiency benefits could further develop as the use of longer power durations, beyond 180 degrees even could be envisioned.